Correlation of the first reduction potential of selected radiosensitizers determined by cyclic voltammetry with theoretical calculations

2011 ◽  
Vol 76 (8) ◽  
pp. 937-946 ◽  
Author(s):  
Miroslav Gál ◽  
Viliam Kolivoška ◽  
Marta Ambrová ◽  
Ján Híveš ◽  
Romana Sokolová
Keyword(s):  
Experimental Study ◽  
Cyclic Voltammetry ◽  
Radical Anion ◽  
Reduction Potential ◽  
Theoretical Calculations ◽  
Dft Method ◽  
Basis Set ◽  
Radical Anions ◽  
Electron Affinities ◽  
Electron Reduction

Radiosensitizers are drugs that make cancer cells more sensitive to radiation therapy. The cytotoxic properties of such compounds are due to the fact that in the cell these compounds undergo one-electron reduction to generate radical anions. Therefore, their theoretical and/or experimental study is of high interest. To determine the correlation between reduction potential determined by cyclic voltammetry measurements and some physicochemical properties of selected radiosensitizers theoretical calculations of electron affinities based on the DFT method with B3LYP functional at the level of 6-311++G** basis set in vacuum were utilized. Very good correlation was found between electron affinities of radiosensitizers and their reduction potential and so called E71 potential that account for the energy necessary to transfer the first electron to an electroactive group at pH 7 in aqueous medium to form a radical anion.

scholarly journals One-Electron Reduction Potentials: Calibration of Theoretical Protocols for Morita–Baylis–Hillman Nitroaromatic Compounds in Aprotic Media

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2129 ◽  
Author(s):  
Amauri Francisco da Silva ◽  
Antonio João da Silva Filho ◽  
Mário Vasconcellos ◽  
Otávio Luís de Santana
Keyword(s):  
Cyclic Voltammetry ◽  
Biological Activity ◽  
Chemical Structure ◽  
Reduction Potential ◽  
Chemical Reactivity ◽  
Nitroaromatic Compounds ◽  
Reduction Potentials ◽  
Electron Reduction ◽  
The One ◽  
Antileishmanial Activities

Nitroaromatic compounds—adducts of Morita–Baylis–Hillman (MBHA) reaction—have been applied in the treatment of malaria, leishmaniasis, and Chagas disease. The biological activity of these compounds is directly related to chemical reactivity in the environment, chemical structure of the compound, and reduction of the nitro group. Because of the last aspect, electrochemical methods are used to simulate the pharmacological activity of nitroaromatic compounds. In particular, previous studies have shown a correlation between the one-electron reduction potentials in aprotic medium (estimated by cyclic voltammetry) and antileishmanial activities (measured by the IC50) for a series of twelve MBHA. In the present work, two different computational protocols were calibrated to simulate the reduction potentials for this series of molecules with the aim of supporting the molecular modeling of new pharmacological compounds from the prediction of their reduction potentials. The results showed that it was possible to predict the experimental reduction potential for the calibration set with mean absolute errors of less than 25 mV (about 0.6 kcal·mol−1).

scholarly journals Mutually Isomeric 2- and 4-(3-Nitro-1,2,4-triazol-1-yl)pyrimidines Inspired by an Antimycobacterial Screening Hit: Synthesis and Biological Activity against the ESKAPE Panel of Pathogens

Antibiotics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 666
Author(s):  
Sergey Chuprun ◽  
Dmitry Dar’in ◽  
Elizaveta Rogacheva ◽  
Liudmila Kraeva ◽  
Oleg Levin ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Antibacterial Activity ◽  
Reduction Potential ◽  
Gram Negative ◽  
Reduction Potentials ◽  
Apparent Correlation ◽  
Electron Reduction ◽  
Activity Loss ◽  
Eskape Pathogens ◽  
Bioactivity Profile

Starting from the structure of antimycobacterial screening hit OTB-021 which was devoid of activity against ESKAPE pathogens, we designed, synthesized and tested two mutually isomeric series of novel simplified analogs, 2- and 4-(3-nitro-1,2,4-triazol-1-yl)pyrimidines, bearing various amino side chains. These compounds demonstrated a reverse bioactivity profile being inactive against M. tuberculosis while inhibiting the growth of all ESKAPE pathogens (with variable potency patterns) except for Gram-negative P. aeruginosa. Reduction potentials (E1/2, V) measured for selected compounds by cyclic voltammetry were tightly grouped in the −1.3–−1.1 V range for a reversible single-electron reduction. No apparent correlation between the E1/2 values and the ESKAPE minimum inhibitory concentrations was established, suggesting possible significance of other factors, besides the compounds’ reduction potential, which determine the observed antibacterial activity. Generally, more negative E1/2 values were displayed by 2-(3-nitro-1,2,4-triazol-1-yl)pyrimidines, which is in line with the frequently observed activity loss on moving the 3-nitro-1,2,4-triazol-1-yl moiety from position 4 to position 2 of the pyrimidine nucleus.

Tests of second-generation and third-generation density functionals for electron affinities of the alkylthio radicals

2014 ◽  
Vol 13 (04) ◽  
pp. 1450030 ◽  
Author(s):  
Aifang Gao ◽  
Aiguo Li
Keyword(s):  
Dft Method ◽  
Absolute Error ◽  
Molecular Structures ◽  
Basis Set ◽  
Density Functionals ◽  
Electron Affinities ◽  
Generalized Gradient ◽  
Experimental Values ◽  
P Type ◽  
Good Agreement

The molecular structures and electron affinities of the R – S / R – S -( R = CH 3, C 2 H 5, n- C 3 H 7, n- C 4 H 9, n- C 5 H 11, i- C 3 H 7, i- C 4 H 9, t- C 4 H 9) species have been studied using 17 pure and hybrid density functionals (five generalized gradient approximation (GGA) methods, six hybrid GGAs, one meta GGA method and five hybrid meta GGAs). The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted by DZP++. The geometries are fully optimized with each DFT method and discussed. Harmonic vibrational frequencies are found to be within 3.5% of available experimental values for most functionals. Three different types of the neutral-anion energy separations have been presented. The theoretical electron affinities of alkylthio radicals are in good agreement with the experiment data. The M06 method is very good for the adiabatic electron affinity calculations, and the average absolute error is 0.0439 eV. The HCTH method performs better for EA prediction. The M06-HF, mPWPW91, VSXC and B98 are also reasonable. The most reliable adiabatic electron affinities are predicted to be 1.864 eV ( CH 3 S ), 1.946 eV ( C 2 H 5 S ), 1.959 eV (n- C 3 H 7 S ), 1.970 eV (n- C 4 H 9 S ), 1.982 eV (n- C 5 H 11 S ), 2.053 eV (i- C 3 H 7 S ), 1.991 eV (i- C 4 H 9 S ) and 2.100 eV (t- C 4 H 9 S ) at the M06/DZP++ level of theory, respectively.

Molecular structure and relative proton and electron affinities of isomeric nitroimidazoles

1989 ◽  
Vol 67 (10) ◽  
pp. 1666-1671 ◽  
Author(s):  
Salim F. Farah ◽  
Robert A. McClelland ◽  
Michael R. Peterson ◽  
Imre G. Csizmadia
Keyword(s):  
Dipole Moment ◽  
Radical Anion ◽  
Dipole Moments ◽  
Rotational Transition ◽  
Basis Set ◽  
Electron Affinities ◽  
Conjugate Acid ◽  
Biological Effectiveness ◽  
Group Rotation ◽  
Relative Change

The isomeric 2-nitro, 4-nitro, and 5-nitroimidazoles have been studied in their planar ground state, C—NO2 rotational transition state, 3-H protonated conjugate acid and radical anion forms, with abinitio computations at the split-valence 3-21G basis set level. The stabilities of the parent compounds follow the order 5-NO2 ~ 4-NO2 > 2-NO2. In solution 4-nitro is more stable than 5-nitro; the calculations suggest that this is a solvation effect, since the 4-nitro isomer has a considerably higher dipole moment. Barriers for nitro group rotation range from 10 to 16 kcal/mol. However, the relative change in dipole moment during the rotation is small, suggesting that dipole moments of nitroimidazoles are determined mainly by inductive effects, with resonance interactions being relatively unimportant. This conclusion is supported by calculations of molecular electrostatic potentials of the planar and rotated forms. Electron affinities follow the order [Formula: see text], closely matching the order of biological effectiveness of nitroimidazole radiosensitizers. This is consistent with suggestions that the "nitro:nitro radical anion" redox cycle is an important determinant of biological activity. Keywords: nitroimidazole, abinitio computation, rotational barrier, proton affinity, electron affinity.

scholarly journals Conformational isomerism of 1-butene secondary ozonide as studied by means of matrix isolation infrared absorption spectroscopy

2012 ◽  
Vol 10 (5) ◽  
pp. 1647-1656
Author(s):  
Simona Strazdaite ◽  
Ruta Bariseviciute ◽  
Justinas Ceponkus ◽  
Valdas Sablinskas
Keyword(s):  
Absorption Spectroscopy ◽  
Infrared Absorption ◽  
Theoretical Calculations ◽  
Matrix Isolation ◽  
Dft Method ◽  
Basis Set ◽  
Infrared Absorption Spectroscopy ◽  
Spectral Bands ◽  
Secondary Ozonide ◽  
The Matrix

AbstractTheoretical calculations of structures, stability and vibrational spectra of 1-butene secondary ozonide (SOZ) conformers were performed using DFT method B3LYP with a 6-311++G(3df, 3pd) basis set. The calculations predict six staggered structures of 1-butene SOZ. The FTIR spectra of 1-butene SOZ isolated in Ar, N2 and Xe matrices were recorded. It was found that nitrogen is the best suited for the matrix isolation of 1-butene SOZ. The bandwidth of the spectral bands of the ozonide isolated in nitrogen was as narrow as 2 cm−1. For the first time the existence of five conformers of 1-butene SOZ were confirmed experimentally by means of matrix isolation infrared absorption spectroscopy. The equatorial gauche (∠OCCC=−66.1°) conformer was proved theoretically and experimentally to be the most stable. It was found that due to high potential barriers of the conformational transitions annealing of the matrix is useless for the assignment of spectral bands to various conformers of 1-butene SOZ. Using the hot nozzle technique the van’t Hoff experimental plots were made for three additional conformers of 1-butene SOZ and experimental ΔH values for these additional conformers were established. The crystallization problems of 1-butene SOZ are discussed which accounts for the rich conformational diversity of the ozonide as well as high conformational barriers for axial-equatorial transitions.

scholarly journals 4-{[4-(Dimethylamino)benzylidene]amino}-5-methyl-4H-1,2,4-triazole-3-thiol as Corrosion Inhibitor for 316 Stainless Steel in 2.5 M Sulphuric Acid: An Experimental and Theoretical Investigation

2020 ◽  
Vol 32 (5) ◽  
pp. 1015-1025
Author(s):  
N. Shet ◽  
R. Nazareth ◽  
P. Krishna Murthy ◽  
P.A. Suchetan
Keyword(s):  
Stainless Steel ◽  
Inhibition Efficiency ◽  
Theoretical Calculations ◽  
Dft Method ◽  
Langmuir Adsorption Isotherm ◽  
Basis Set ◽  
X Ray ◽  
Langmuir Adsorption ◽  
316 Stainless Steel ◽  
Stainless Steel 316

The corrosion inhibition competence of 4-{[4-(dimethylamino)benzylidene]amino}-5-methyl-4H-1,2,4-triazole-3-thiol (DBTT) on 316 stainless steel (316 SS) in 2.5 M H2SO4 was studied using various electrochemical as well as weight-loss measurements. The alloy surface was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Concentration effect on inhibition efficiency was investigated by varying concentration from 5 to 2000 ppm in the temperature range 30-60 °C. Results indicated mixed-type inhibitory action of DBTT. The efficiency increased with the raise in concentration of DBTT and temperature, reaching a highest of 92.4 % at 60 °C. Langmuir adsorption isotherm is obeyed. Calculation of different thermodynamic factors suggests that the adsorption is via both physisorption and chemisorption. In addition to these, several global reactivity parameters were calculated using DFT method at B3LYP/6-311++(d,p) basis set. Theoretical calculations are in good concurrence with the experimental results.

Solid solution of two diastereomers of [3a(R,S),7a(R,S)]-3-[(1′R)-1-phenylethyl]perhydro-1,3-benzothiazol-2-iminium chloride

2010 ◽  
Vol 66 (6) ◽  
pp. 678-686 ◽  
Author(s):  
Agnieszka Plutecka ◽  
Urszula Rychlewska ◽  
Natalia Prusinowska ◽  
Jacek Gawroński
Keyword(s):  
Solid Solution ◽  
Electronic Structure ◽  
Solid State ◽  
Natural Bond Orbital ◽  
Theoretical Calculations ◽  
Dft Method ◽  
Energy Difference ◽  
Basis Set ◽  
Asymmetric Unit ◽  
Crystallographic Site

A mixture of two diastereomers with the configurations (3aS,7aS,1′R) and (3aR,7aR,1′R) forms co-crystals in which there is one unique molecule in the asymmetric unit, but the molecule displays disorder which is a result of the presence of the two diastereomers at the same crystallographic site. Theoretical calculations carried out by the DFT method with the 6-311++G(2df,p) basis set allowed for the estimation of the energy difference between the two diastereomers both in the isolated and the solid state, while the natural bond orbital (NBO), Mulliken, natural population (NPA) and CHelpG analyses helped to establish the electronic structure of the thazolidin-2-imine fragment.

X-ray and DFT Investigation of (E)-4-bromo-5-methoxy-2-((o-tolylimino)methyl)phenol Compound

2018 ◽  
pp. 454-461
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Population Analysis ◽  
Diffraction Method ◽  
Dft Method ◽  
Basis Set ◽  
X Ray Diffraction ◽  
Mulliken Population ◽  
Charge Delocalization ◽  
X Ray

(E)-4-bromo-5-methoxy-2-((o-tolylimino)methyl)phenol was investigated by experimental and theoretical methodologies. The solid state molecular structure was determined by X-ray diffraction method. All theoretical calculations were performed by density functional theory (DFT) method by using B3LYP/6-31G(d,p) basis set. The titled compound showed the preference of enol form, as supported by X-ray diffraction method. The geometric and molecular properties were compaired for both enol-imine and keto-amine forms for title compound. Stability of the molecule arises from hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond has been analyzed using natural bond orbital (NBO) analysis. Mulliken population method and natural population analysis (NPA) have been studied. Also, condensed Fukui function and relative nucleophilicity indices calculated from charges obtained with orbital charge calculation methods (NPA). Molecular electrostatic potential (MEP) and non linear optical (NLO) properties are also examined.

The one- and two-electron reduction of 2-thioriboflavin by radical anions of CO2 and dithiothreitol

1986 ◽  
Vol 64 (1) ◽  
pp. 67-70 ◽  
Author(s):  
Parminder S. Surdhar ◽  
David A. Armstrong ◽  
Vincent Massey
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Radical Anion ◽  
Pulse Radiolysis ◽  
Continuous Production ◽  
Radical Anions ◽  
Reduction Step ◽  
Equivalence Point ◽  
Electron Reduction ◽  
The One

The one- and two-electron reductions of 2-thioriboflavin with[Formula: see text] and cyclic disulphide anion of dithiothreitol [Formula: see text] have been studied by the steady state γ and pulse radiolysis techniques. The [Formula: see text] radical reacted with 2-thioriboflavin to give the neutral semiquinone (•FlH) and the radical anion (•Fl−) at pH 5 and 10 respectively. The pK of the •FlH radical was determined to be 7.4. In the case of the anion, the 2-thioriboflavin spectrum is similar in shape to that of FAD radical anion, but red shifted by 40–50 nm. Red shifts are also seen in the neutral •FlH form for the 370-nm peak and 580-nm shoulder. However, in addition, there is strong enhancement of the absorbance at 500 nm. The spectrum of 2-thioriboflavin semiquinone produced in the presence of 2–5 mM dithiothreitol was perturbed, as was observed previously for unsubstituted flavin semiquinones in the presence of sulphydryls. The rate constants for the initial one-electron reduction step viz: [Formula: see text] were 4.0 ± 0.5 × 109 M−1 s−1 and 1.3 ± 0.2 × 109 M−1 s−1 at pH 7 and 10 respectively. The corresponding rate for the reaction of [Formula: see text] with 2-thioriboflavin at pH 7 was determined to be 2.4 ± 0.2 × 109 M−1 s−l. The continuous production of [Formula: see text] radicals by γ radiolysis reduced 2-thioriboflavin to the dihydro form, and the flavin was regenerated on the addition of air. The[Formula: see text] radical also effected a two-electron reduction. However, in this case, if the process was taken beyond the equivalence point, the dihydroflavin spectrum was bleached and the oxidized flavin could not be recovered.

Theoretical calculations of intramolecular hydrogen bond of the 2-Amino-2, 4, 6-cycloheptatrien-1-one in the gas phase and solution: Substituent effects and their positions

2016 ◽  
Vol 15 (07) ◽  
pp. 1650063 ◽  
Author(s):  
Narges Khatoon Attaran Toosy ◽  
Heidar Raissi ◽  
Maryam Zaboli
Keyword(s):  
Hydrogen Bond ◽  
Gas Phase ◽  
Intramolecular Hydrogen Bond ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Substituent Effects ◽  
Dft Method ◽  
Basis Set ◽  
Parent Molecule ◽  
Intramolecular Hydrogen

The density functional theory (DFT) method with 6-311[Formula: see text]G[Formula: see text] basis set has been used to calculate the intramolecular hydrogen bond, molecular structure, vibrational frequencies, nuclear quadrupole resonance (NQR) parameters, 1HNMR, and resonance parameters of 2-Amino-2, 4, 6-cycloheptatrien-1-one (2-amino tropone) and its 18 derivatives in 5 positions. The natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses have been studied. The strongest and weakest hydrogen bonds exist for NO2 substituent in R3 position and OH in R7 position, respectively. In general, the substituted systems in position 3 indicate the stronger hydrogen bond in comparison with the parent molecule (R[Formula: see text]H), while, it is comparatively weaker for position 5. The energy of the N-H[Formula: see text]O interaction is found to be medium in strength ([Formula: see text][Formula: see text]kJ mol[Formula: see text] to [Formula: see text][Formula: see text]kJ mol[Formula: see text]). The low [Formula: see text], positive [Formula: see text] values and [Formula: see text] show that the nature of O [Formula: see text] H bonding is electrostatic. Also, our theoretical results show that the hydrogen bond strength in solution phase and the first singlet excited state is weaker in comparison with the gas phase ground state.

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